AB1553 INVESTIGATION OF FACTORS ASSOCIATED WITH PET/CT EXPERIENCE AND DIAGNOSTIC VALUE IN RHEUMATOLOGY PRACTICE
Authors: P. Akyüz Dağli, S. C. Güven, N. Coşkun, Ö. Karakaş, B. Armagan, K. Gok, I. Dogan, Y. Maraş, Ş. Türkölmez, S. Erten
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> The use of PET/CT is becoming more common in the elucidation of inflammatory processes in which the underlying cause cannot be determined by conventional examinations. Although PET/CT is an effective method for detecting inflammatory foci, the precise diagnosis may not be obtained in all cases. <h3>Objectives</h3> In this study, it was aimed to examine the factors that can predict the differential diagnosis value of PET/CT by retrospectively scanning patients who underwent PET/CT for inflammation of unknown origin(IUO) in rheumatology practice. <h3>Methods</h3> Demographic, clinical and laboratory information of the patients followed up in our clinic and who underwent PET/CT for differential diagnosis were enrolled. Whether they were diagnosed after PET/CT and during the follow-up period, and their diagnoses were examined. <h3>Results</h3> A total of 132 patients were included in the study. A previous diagnosis of rheumatic disease was present in %28.8 of the patients, and a history of malignancy was present in %2.3. The patients were divided into three groups: Group 1 patients with increased FDG uptake in PET/CT and the diagnosis confirmed by PET/CT, group 2 patients with increased FDG uptake in PET/CT but the diagnosis of was not confirmed, and group 3 patients without increased FDG uptake in PET/CT. Increased FDG uptake in PET/CT was detected in %73 of the patients. While PET/CT helped the diagnosis in 47(%35.6) patients(Group 1), it did not help the diagnosis in 85(%64.4) (Group 2,3). Thirty-one (%65.9) of the diagnosed patients were diagnosed with a rheumatologic disease. When the 3 groups were compared, male gender, advanced age, CRP levels, presence of constitutional symptoms, SUVmax values and number of different organs with increased FDG uptake were higher in Group 1. %66 and %74 of the patients in groups 2 and 3 were not diagnosed during the follow-up period. No patient in group 3 was diagnosed with malignancy during follow-up. <h3>Conclusion</h3> PET/CT has high diagnostic value when combined with clinical and laboratory in the diagnosis of IUO. Our study revealed that various factors can affect the diagnostic value of PET/CT. Although detection of involvement in PET/CT is not always diagnostic, it was an important finding that no malignancy was detected in the follow-up in any patient without involvement. <h3>References</h3> [1]Schönau, V., Vogel, K., Englbrecht, M., Wacker, J., Schmidt, D.,... &amp; Schett, G. (2018). The value of 18F-FDG-PET/CT in identifying the cause of fever of unknown origin (FUO) and inflammation of unknown origin (IUO): data from a prospective study. <i>Annals of the Rheumatic Diseases</i>, <i>77</i>(1), 70-77. [2]Wang, Q., Li, Y. M., Li, Y., Hua, F. C.,... &amp; Wang, X. M. (2019).18F-FDGPET/CT in fever of unknown origin and inflammation of unknown origin: a Chinese multi-center study. <i>European journal of nuclear medicine and molecular imaging</i>, <i>46</i>(1), 159-165. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.